Gas turbine engines are used extensively in high performance aircraft and they employ fans, compressors, combustors and turbines and during operation they generate energies and air flows that impact the performance of the engine's systems. A gas turbine may employ one or more combustors that serve as the fuel preparation and ignition chambers for generating the temperature rise which is required to drive the turbine blades. Typical combustors may use inner and outer liners that define an annular combustion chamber in which the fuel and air mixtures are combusted. The inner and outer liners are radially offset from the combustor casings such that inner and outer passage ways are defined between the respective inner and outer liners and casings.
In order to improve the thrust and fuel consumption of gas turbine engines, i.e., the thermal efficiency, it is necessary to use high compressor exit pressures and combustion exit temperatures. Higher compressor pressures also give rise to higher compressor exit temperatures supplied to the combustion chamber, which results in a combustor chamber experiencing much higher temperatures than are present in most conventional combustor designs.
A need exists to provide effective cooling of the combustion chamber walls. Various cooling methods have been proposed including the provision of a doubled walled combustion chamber whereby cooling air is directed into a gap between spaced outer and inner walls, thus cooling the inner wall. This air is then exhausted into the combustion chamber through apertures in the inner wall. The inner wall may be comprised of a number of heat resistant tiles.
Combustion chamber walls which comprise two or more layers are advantageous in that they only require a relatively small flow of air to achieve adequate wall cooling. However, hot spots may form in certain areas of the combustion chamber wall. This problem is heightened as temperatures within the combustion chamber which can exceed 3,500 degrees F. Such harsh environmental conditions may prematurely reduce the life of the liner of the combustor. In addition, loss of tile attachment and subsequent component distress remains an engineering challenge in current combustor technology.